Preparation,crystal strucures,electrochemical and spectroscopic properties of bis(2,2'-bipyridine) ruthenium(II) complexes containing 8-(diphenylphosphino) quinoline or 2-(diphenylphosphino)pyridine

摘要

Mixed-ligand bis(2,2'-bipyridine)ruthenium(II) complexes containing a hybrid donor-type P-N ligand of 8-(diphenylphosphino)quinoline (Ph_2Pqn) or 2-(diphenylphopshino)pyridine (Ph_2Ppy),[Ru(bpy)_2(Ph_2Pqn or Ph_2Ppy)](PF_6)_2 (1 or 2;bpy=2,2'-bipyridine),have been prepared.The X-ray crystal structure aalyses of 1 and 2 revealed that Ph_2Pqn and Ph_2Ppy act as a bidentate ligand to forma five-and four-membered chelate ring,respectivley.The four-membered chelate ring formed by Ph_2Ppy has a very smallbite angle (P(1)-Ru-N(1):68.4(1)deg),but the Ru~(II)(bpy)_2 moiety in 2 has a typically strain-free structure.On the other hand,in the Ph_2Pqn complex 1,one of the bpy planes is skewed remarkably from the Ru coordination plane due to an intramolecular steric interaction with a phenyl ring of Ph_2Pqn.The redox potentials and the ~1MLCT transition energies of the Ph_2Pqn and Ph_2Ppy complexes (1 and 2) were not so different from the averaged values of those of the corresponding 1,2-bis(diphenylphosphino)benzene (dppb) and 1,10-phenanthroline (phen) complexes,[Ru(bpy)_2 (dppb or phen)](PF_6)_2 (3 or4).These facts indicate that the electronic asymmetry inherently present in Ph-2Pqn and Ph_2Ppy does not affect remarkabley the ground state propertiesof the complexes.However,unlike complexes 2-4,the Ph_2Pqn complex 1 in EtOH/MeOH(4:1) glass at 77K exhibited a noveldual emission,giving a biexponential emission decay.The shorter-lived emission is attributable to the bpy-based ~3MLCT emission,similar to the other Ru~(II)-polypyridine complexes,while the longer-lived emission can probably be assigned as arising from the quinoline-based ~3(pi-pi*) excited state.